The presence of antibiotics in water used for fish farming is a growing global concern because it can lead to the development of drug-resistant bacteria that threaten human health. In a study published in the journal Environmental Science and Pollution Research, authors Samuel Moles, Rosa Mosteo, Francisca Romero-Sarria, Patricia García-Muñoz, and Jorge Rodríguez-Chueca explored a sustainable solution using pine bark. The team turned this forestry waste into biochar, a charcoal-like substance, to see if it could act as a sponge to soak up tetracycline, one of the most common antibiotics used in the aquaculture industry.

The researchers discovered that the way the biochar is prepared makes a massive difference in its cleaning power. By activating the pine-bark biochar with carbon dioxide at 800 degrees Celsius, they were able to create a material with a surface area of 583 square meters per gram. This is significantly more effective than using steam for activation, which produced a surface area of only 385 square meters per gram. The larger surface area provided by the carbon dioxide treatment creates a vast network of microscopic pores that are perfectly sized to catch and hold antibiotic molecules.

When tested in real aquaculture wastewater—which contains various salts and organic matter that can often interfere with water treatment—the biochar performed better than expected. In these real-world conditions, the material achieved between 80 and 100 percent removal of tetracycline. The study found that the natural minerals and salts in the fish farming water actually helped the antibiotic molecules stick to the biochar surface more effectively. This is a significant finding because many water treatment technologies work well in a laboratory with pure water but fail when faced with the complexity of actual environmental samples.

The effectiveness of the biochar was also heavily influenced by the acidity or alkalinity of the water. The best results were seen under slightly alkaline conditions, specifically at a pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More of 9, where the chemical interactions between the biochar and the antibiotic were strongest. This is particularly useful because aquaculture systems often operate in this range. The researchers noted that even though both the biochar and the antibiotic carry negative charges in these conditions, other forces like hydrogen bonding and specialized chemical attractions are strong enough to overcome any natural repulsion and secure the pollutants.

To further enhance the cleaning process, the team combined the biochar with a low dose of an oxidant called peroxymonosulfate. This combination created a synergistic effect that reached 99 percent removal even more quickly. The biochar acts as a catalyst, helping the oxidant break down the antibiotics into harmless components while simultaneously trapping them on its surface. This dual-action approach ensures that the antibiotics are not just moved from the water to the biochar but are actively being destroyed, reducing the risk of any future contamination.

Ultimately, this research demonstrates that common waste products like pine bark can be transformed into high-value environmental tools. By using carbon dioxide to “supercharge” the biochar, scientists have developed a low-cost and metal-free method to protect aquatic ecosystems. This approach offers a green alternative to traditional wastewater treatment plants, which are often not equipped to handle pharmaceutical pollutants. As the aquaculture industry continues to grow, sustainable materials like pine-bark biochar will be essential for maintaining clean water and preventing the spread of antibiotic resistance in the environment.

Source: Moles, S., Mosteo, R., Romero-Sarria, F., García-Muñoz, P., & Rodríguez-Chueca, J. (2026). Upcycling pine-bark into powerful adsorbents: Tetracycline removal from aquaculture effluents combining biochar and advanced oxidation processes. Environmental Science and Pollution Research.